universal anode reaction for water electrolysis, carbon dioxide reduction, and metalair batteries, which usually requires the use of noble metal catalyst due to the sluggish kinetics. [1] However, due to the high cost and scarcity, large-scale application of noble metals is greatly restricted. Therefore, the development of non-noble metal catalysts with high efficiency and low cost is of great importance. In particular, transition metal-based layer double hydroxides (LDHs) have attracted extensive attention because of their facile synthesis and adjustable composition. [2] The OER performance of LDHs is limited by active sites and poor intrinsic activity. [3] Moreover, due to their semiconductor characteristics, a Schottky barrier may be formed when contacting the conductive substrate, which greatly hinders the charge transfer. [4] A variety of strategies, including size modulation, composite with conductive materials, heteroatomic doping, defect engineering, and interface engineering, have been investigated to further regulate the OER performance of LDHs. [5] It is noteworthy that adjusting the electronic structure of the catalysts can optimize the adsorption energy of the intermediates and improve the reaction kinetics. [5c] In this regard, the construction of p-n heterojunction is a promising strategy to regulate the local electronic structure of catalytically active sites, as the difference of Fermi level (E f ) between n-type semiconductor and p-type semiconductor results in the spontaneous flow of electrons at the interface to achieve thermal equilibrium. As a consequence, the activity, selectivity, and stability can be substantially improved by binary catalysts when compared with single-component catalysts. For example, the p-n junction in FeNi-LDH/CoP with positively charged FeNi-LDH in the space-charge region could greatly improve the OER performance, [6] and the formed CuO@CoOOH p-n heterojunction could remarkably modify the electronic properties and serve as an excellent OER catalyst. [7] In addition to ameliorating the catalyst materials, the emergence of intensification strategies by external fields such as gravity field, light field, ultrasonic, and electric field, has become a new trend in the field of electrochemistry, which can effectively improve the mass transfer on the electrode surface and change the reaction kinetics. [8] Interestingly, the latest research confirms that coupling the magnetic field with electrochemistry Here, a strategy to regulate the electron density distribution by integrating NiFe layered double hydroxides (NiFe-LDH) nanosheets with Co 3 O 4 nanowires to construct the NiFe-LDH/Co 3 O 4 p-n heterojunction supported on nickel foam (NiFe-LDH/Co 3 O 4 /NF) for electrocatalytic oxygen evolution reaction (OER) is proposed. The p-n heterojunction can induce the charge redistribution in the heterogeneous interface to reach Fermi level alignment, thus modifying the adsorption free energy of *OOH and improving the intrinsic activity of the catalyst. As a result, NiFe-LDH/Co 3 ...
